A localized collection of pus in a cavity formed by the disintegration of tissues usually from infection. It is a defensive reaction by the body’s immune system to prevent the spread of infectious or foreign materials (e.g. bacteria, parasites, splinters) to other parts of the body.

A cholinergicneurotransmitter in the central and autonomic nervous systems; it has many functions, including playing an important role in memory and as a stimulatory neurotransmitter which causes muscles to contract when released from nerves.

The electrical signal which rapidly propagates along the axon of nerve cells as well as over the surface of some muscle and glandular cells and leads to stimulation of desired effect. It is the result of a change in flow of ions across the membrane due to voltage-activated ion channels.